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Thread: Almost a Goblin

  1. #1
    Join Date
    19th January 2009
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    3,394

    Almost a Goblin

    I am building a Goblin upscale based on the new 7.5" Blue Tube 2.0. I'm calling it 'Almost a Goblin' as there are two deviations from scale. First, I'm using a PML nose cone that is the correct length but not quite the shape of an upscale BNC-55AO. Secondly, I'm increasing the scale 53" body length to 60" so I can use motors up to 48" long. The rocket will have a single 98mm motor mount.


  2. #2
    Join Date
    19th January 2009
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    First, I built an E-bay into a section of 6" coupler. The e-bay will vent into the main body and the main body will have vents a way down the airframe. I know I'm taking a chance that the apogee event pressure will effect the altimeter. From my experience, the Perfectflite MAWDs do not respond to an event that is shorter than the sampling interval. Do to the vent arrangement, I cannot just twist and tape the power wires so I built a screw switch that can be activated with an allen wrench through a hole in the airframe. The e-bay is my standard construction with a 1/2" threaded rod through the center and eye nuts on each end. The pictures show the inside of the e-bay, screw switch in off and on positions, switch wired to altimeter, and an overall view of the e-bay.

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  3. #3
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    Next, I modified a 7.5-6.0 centering ring to fit the nose cone and epoxied it into place, A 5/16" forged eyebolt was potted into the tip of the nose for recovery attachment. Then I installed a length of 6" body tube. There is plenty of room for wadding, shock cord, and 15' parachute. The e-bay inserts into the 6" BT and is held with 3 4-40 nylon shear pins. The entire nose assembly, complete with chute but without altimeter, weighs 8 lb.
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  4. #4
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    19th January 2009
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    The Blue Tube main airframe has arrived along with the 3/8" baltic birch for the fins. I'll be working on the rest of the rocket gradually over the next couple of weeks.

  5. #5
    Join Date
    18th January 2009
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    Looks like it's going to be a fun project. you gotta love a goblin...almost!
    Stickershock23.com

    FACEBOOK

    Stickershock23@gmail.com

    "Exceed Your Visions":madnote:

  6. #6
    Join Date
    19th January 2009
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    I've gotten quite a bit of work done on the rocket over the last week. Fins were cut from the 3/8" plywood and the edges rounded. A 12" piece of body tube was cut and a coupler epoxied in. Then the fin slots were cut in this section. One centering ring was sanded down to fit inside the coupler.
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  7. #7
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    I attach my recovery harness to the top centering ring so I added 3 layers of 7 oz cloth to each side. Then the forged eyebolt is mounted with fender washers to spread the load. After epoxying the forward 2 centering rings to the motor tube, it's installed first into the lower portion of the airframe, then the upper section is added.
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  8. #8
    Join Date
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    The rear CR is removable so I can add fillets to the internal fin joints. To help prevent the front CR from ripping out in the case of a high speed deployment, a short section of tube was cut and slitted. This was epoxied in front of the centering ring. Next step - tack the fins in place. Finally, I put the nose cone on to see what it looks like The body section, including the shock cord currently weighs 10 lb. Now for the time consuming part - fillets, priming, sanding, and painting. I'm expecting the final dry weight to be about 25 lb.
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  9. #9
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    Hey, that does look like Almost a Goblin! Cool, Tom!75mm or 98mm motor hole?

    Can't wait to see it in person!
    Chute Happens!!
    NAR 86940 L2
    TRA 12270 L3 09-01-12
    KF4GUL
    TeleTubby Fan, Unofficial King of Namby-Pamby Land:tongue:

  10. #10
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    Quote Originally Posted by Pantherjon View Post
    Cool, Tom!75mm or 98mm motor hole?
    98 of course. You can always adapt down...

  11. #11
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    Is it done yest? Is it done yet? Is it done yet?
    Chute Happens!!
    NAR 86940 L2
    TRA 12270 L3 09-01-12
    KF4GUL
    TeleTubby Fan, Unofficial King of Namby-Pamby Land:tongue:

  12. #12
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    Quote Originally Posted by Pantherjon View Post
    Is it done yest? Is it done yet? Is it done yet?
    It's got a couple of coats of primer on it. Waiting for weather suitable for painting (on a day I'm not at work - beautiful weather the last couple of work days)

  13. #13
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    17th February 2010
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    First post here

    I know this will date me but here's a reminder of the original paint scheme. By far one of my most favorite models. I think I know what I'll build for L2
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  14. #14
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    Quote Originally Posted by degreaser View Post
    First post here

    I know this will date me but here's a reminder of the original paint scheme. By far one of my most favorite models. I think I know what I'll build for L2
    It was my favorite back in the early '70s when a D was a BIG motor. Mine will look like the attached picture but about twice the size of the large one (one black fin).
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  15. #15
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    24th February 2010
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    Brewster,NY
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    Lightbulb

    That really looks like a Goblin Rocket Junkie. I also like the last picture. Look at the size compairtions. One big and one small.

  16. #16
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    24th February 2010
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    Brewster,NY
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    Both rockets also Tom.

  17. #17
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    24th February 2010
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    Is the Goblin really done? Is the Goblin really done?

  18. #18
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    23rd February 2009
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    Northern NJ
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    Goblin???

    I think he had to stop & help Pantherjon with his unboxing thread...




    JD



    Quote Originally Posted by Rocketeer41 View Post
    Is the Goblin really done? Is the Goblin really done?

  19. #19
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    Quote Originally Posted by Pantherjon View Post
    Is it done yest? Is it done yet? Is it done yet?
    Finally
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  20. #20
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    Awesome!
    ~Don
    Tripoli 12614
    L3

  21. #21
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    18th January 2009
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    Quote Originally Posted by Rocketjunkie View Post
    Finally

    BEAUTIFUL! gotta love a Goblin!
    Stickershock23.com

    FACEBOOK

    Stickershock23@gmail.com

    "Exceed Your Visions":madnote:

  22. #22
    Join Date
    20th March 2009
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    534
    Quote Originally Posted by Rocketjunkie View Post
    The e-bay will vent into the main body and the main body will have vents a way down the airframe. I know I'm taking a chance that the apogee event pressure will effect the altimeter.
    Just to double check, is the inside of the altimeter bay completely shielded from the ejection gasses? I'm not clear on the venting arrangement.

    The only reason I mention this is that I looked over one of my altimeters last week and it looks corroded. I know in the past I had one flight where I didn't properly seal the e-match wire through the bulkhead and I am assuming BP residue got in the bay and subsequently corroded the traces on the altimeter PCB. If that's not what happened, I am at a loss as to why that altimeter looks like it does.

    Obviously you've been flying big stuff for a long time, so I am pretty sure you have it worked out, but I thought I'd mention it.

    Looks great, BTW!

    Sandy.

  23. #23
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    19th January 2009
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    That is one sharp looking Goblin Tom! Stickershock do the decals?
    Chute Happens!!
    NAR 86940 L2
    TRA 12270 L3 09-01-12
    KF4GUL
    TeleTubby Fan, Unofficial King of Namby-Pamby Land:tongue:

  24. #24
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    19th January 2009
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    Quote Originally Posted by Pantherjon View Post
    Stickershock do the decals?
    He sure did. The best weight I can get using a bathroom scale is 24 lb. all except altimeter, wadding, and motor. First flight will probably be on a K700.

  25. #25
    Join Date
    12th September 2009
    Posts
    677

    Thumbs up One of my faves!

    Awesome Tom!

    This is one of my very faves! I did a 2.56 upscale back in '06 and have flown it many time with G80s and plan on putting a "H" in it this season...She needs new paint but still going strong! Gordan turned the nose for me and it was nothing less than perfect.
    I have a 4" in the works and had always wanted to do something "ALOT" bigger and probably will one day. Yours gives me the inspiration to do so!

    Anyways she is a beauty! And you did a FANTASTIC job on her!

    Mike

  26. #26
    Join Date
    12th September 2009
    Posts
    677

    My last Saturday in Manchester,TN

    Here is a shot of mine. It's seen many of flights with G's! But I had her prepped with a H128...She never saw the sky though...No Tripoli prefect there to watch my 4th Cert1!!!! Thanks Walt! LOL

    Anyways though you'd like to look at her...Gordon turned the nose for me back in the spring of '06...The cone is perfect! (well 'cept from scars and scratches) The rest of the rocket ain't so bad either!

    Mike

    Tripoli #5199
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  27. #27
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    Quote Originally Posted by OverLord View Post
    Here is a shot of mine. It's seen many of flights with G's! But I had her prepped with a H128...She never saw the sky though...No Tripoli prefect there to watch my 4th Cert1!!!! Thanks Walt! LOL
    Lookin' good Sorry you didn't get to fly though Mine hasn't flown yet, planning on the May Orangeburg launch. I did mix up a 75/4800 L1100 for a second flight after the initial K700

  28. #28
    Join Date
    19th January 2009
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    Branford, CT
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    Great! job, Post some launch pics.
    Gary Tortora
    TRA 11898 L3

  29. #29
    Join Date
    9th February 2009
    Location
    Oregon, Ohio
    Posts
    101
    Nice job! I had a whole stable of Goblins, from micro-max to 5.5", love that rocket! I'm rebuilding my 5.5" one for the third time, I've broken fins twice on it. This time, it's getting 'glassed!
    Fred Ziegler
    NAR 89151 L3
    TRA 10151 L3
    Fade to Black Rocket Works
    Oregon, Ohio
    http://www.ftbrocketworks.com

  30. #30
    Join Date
    12th September 2009
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    677
    Quote Originally Posted by Rocketjunkie View Post
    Lookin' good Sorry you didn't get to fly though Mine hasn't flown yet, planning on the May Orangeburg launch. I did mix up a 75/4800 L1100 for a second flight after the initial K700
    Hey Tom,
    Your last name wouldn't start with a "B" and end with a "d" would it?
    If it does i just watched some of my old Point 39 Productions LDRS tapes starring a "RocketJunkie"!

    Mike


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